Light emitting device

ABSTRACT

A light emitting device including a board, light emitting elements, a wavelength conversion member, and first and second metal plates. The board has a first surface and an opposite second surface, and is longer in a first direction than in a second direction perpendicular to the first direction. The light emitting elements are mounted on the first surface and are arrayed in a row along the first direction. The wavelength conversion member includes a first portion covering the light emitting elements and a second portion covering the second surface. The light emitting elements includes a first light emitting element located closest to the first metal plate, and a second light emitting element located closest to the second metal plate. The light emitting elements on the first surface are located between a first end surface of the first metal plate and a first end surface of the second metal plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 17/017,676 filed on Sep. 11, 2020, which is acontinuation application of U.S. patent application Ser. No. 16/727,924filed on Dec. 27, 2019, which issued as U.S. Pat. No. 10,801,676, whichis a continuation application of U.S. patent application Ser. No.16/211,140 filed on Dec. 5, 2018, which issued as U.S. Pat. No.10,598,317, which is a continuation application of U.S. patentapplication Ser. No. 15/666,578 filed on Aug. 2, 2017, which issued asU.S. Pat. No. 10,180,213, which is a continuation application of U.S.patent application Ser. No. 15/231,735 filed on Aug. 8, 2016, whichissued as U.S. Pat. No. 9,752,734, which is a continuation applicationof U.S. patent application Ser. No. 13/831,797 filed on Mar. 15, 2013,which issued as U.S. Pat. No. 9,491,813, which is a continuationapplication of U.S. patent application Ser. No. 13/672,713 filed on Nov.9, 2012, which issued as U.S. Pat. No. 9,491,812, which is acontinuation application of U.S. patent application Ser. No. 11/639,062filed on Dec. 14, 2006, which issued as U.S. Pat. No. 8,366,295, andwhich claims priority under 35 U.S.C. § 119 to Japanese PatentApplication No. 2005-364127, filed on Dec. 16, 2005. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a light emitting device.

2. Description of the Related Art

Light emitting devices that employ light emitting elements are small buthigh effective in terms of electric power consumption, and emit vividcolor light. In addition, semiconductor elements are employed as thelight emitting elements, thus, there are no concerns about bulb burnoutand so on. Additionally, semiconductor elements have features, such asexcellent initial drive characteristics, resistance to vibration orON/OFF repeats. Since semiconductor elements have these excellentfeatures, light emitting devices that employ semiconductor lightemitting elements such as light emitting diode (hereinafter,occasionally referred to as “LED”) and semiconductor laser (hereinafter,occasionally referred to as “LD”) have been used as various types oflight sources. For example, a semiconductor light emitting element has alight emitting layer that is laminated on a transparent base member suchas sapphire substrate, GaN substrate, and SiC substrate. In the casewhere the semiconductor light emitting element is formed in asubstantially box shape by cutting, light outgoes not only through theupper surface of the substantially box shape, i.e., its top surface, butalso through the lower surface, i.e., its bottom surface, and the sidesurfaces.

In consideration of the light outgoing surfaces, a lighting apparatuswith a light emitting element as discussed above that is mounted on atransparent conductive portion formed on a transparent board isproposed. In this lighting apparatus, an extending lead is connected tothe light emitting element, and a transparent or translucent resincovers the light emitting element, the transparent board and the lead.This lighting apparatus can emit light in 360-degree directions. SeeJapanese Patent Publication No. 3172947.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a light emittingdevice includes a board having a first surface and a second surfaceopposite to the first surface, the board being longer in a firstdirection than in a second direction perpendicular to the firstdirection in a plan view, and the first surface having a first endportion and a second end portion opposite to each other in the firstdirection. The light emitting device also includes a plurality of lightemitting elements mounted on the first surface of the board, and theplurality of light emitting elements is arrayed in a row along the firstdirection. The light emitting device further includes a wavelengthconversion member adapted to convert wavelength of light emitted fromthe plurality of light emitting elements, and the wavelength conversionmember includes a first portion covering the plurality of light emittingelements and a second portion covering the second surface of the boardin a cross-sectional view. The light emitting device also includes afirst metal plate disposed on the first end portion of the board, and asecond metal plate disposed on the second end portion of the board. Theplurality of light emitting elements includes a first light emittingelement located closest to the first metal plate among the plurality oflight emitting elements, and a second light emitting element locatedclosest to the second metal plate among the plurality of light emittingelements. The first metal plate is electrically connected to the firstlight emitting element via a wire. The first metal plate has a first endsurface facing the first light emitting element, and a second endsurface opposite to the first end surface and exposed from thewavelength conversion member. The second metal plate is electricallyconnected to the second light emitting element via a wire. The secondmetal plate has a first end surface facing the second light emittingelement, and a second end surface opposite to the first end surface andexposed from the wavelength conversion member. The plurality of lightemitting elements on the first surface of the board is located betweenthe first end surface of the first metal plate and the first end surfaceof the second metal plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a light emitting deviceaccording to one embodiment of the present invention;

FIG. 2 is a plan view showing the light emitting device illustrated inFIG. 1;

FIG. 3 is a plan view showing a light emitting device that has metalplates with rounded corners on edges of the metal plates;

FIG. 4 is a cross-sectional view showing a light emitting device with atransparent member being formed in a round shape;

FIG. 5 is a cross-sectional view showing a light emitting device with atransparent member being formed in a rectangular-parallelepiped shape;

FIG. 6 is a cross-sectional view showing a light emitting apparatus witha wavelength conversion member and a transparent member being formedunitarily;

FIG. 7 is a cross-sectional view showing a light emitting device with awavelength conversion member and a sealing member being formedunitarily;

FIG. 8 is a cross-sectional view showing a light emitting device with apackaged light emitting device being installed in a side-up position ina transparent bulb;

FIG. 9 is an enlarged, perspective view showing an installation portionwhere the packaged light emitting device is supported by a support leadillustrated in FIG. 8;

FIG. 10 is a cross-sectional view showing a light emitting device with apackaged light emitting device being installed in a top-side-up positionin a transparent bulb;

FIG. 11 is an enlarged, perspective view showing an installation portionwhere the packaged light emitting device is supported by a support leadillustrated in FIG. 10;

FIG. 12 is a cross-sectional view showing a light emitting device with apackaged light emitting device being installed through elongatedconductor members in a transparent bulb;

FIG. 13 is a cross-sectional view showing a light emitting device withan optical lens being located on the lower side of a transparent board;

FIG. 14 is a plan view showing a light emitting device with a pluralityof light emitting elements being arranged in a matrix shape;

FIG. 15 is a plan view showing a light emitting device with a pluralityof light emitting elements being aligned in a longitudinal direction;and

FIG. 16 is a cross-sectional view showing a light emitting device with alead region being separately provided.

DESCRIPTION OF THE EMBODIMENTS Light Emitting Device

FIGS. 1 and 2 are views showing a light emitting device 100 according toa first embodiment of the present invention. FIG. 1 is a cross-sectionalview showing the light emitting device 100. FIG. 2 is a plan viewshowing the light emitting device 100. FIG. 1 corresponds across-sectional view taken along the line I-I′ of FIG. 2. The lightemitting device 100 illustrated in these Figures includes a lightemitting element 10, a transparent board 20, a pair of conductor members22, a covering member 46, and a pair of metal plates 30. The transparentboard 20 is provided with the light emitting element 10 that is mountedthereon. The pair of conductor members 22 are secured on the transparentsubstrate 20. The covering member 46 is provided with the light emittingelement 10 and the conductor members 22 that are located therein. Thepair of metal plates 30 are inserted into the covering member 46 fromside surfaces of the covering member 46, and are located on the pair ofconductor members 22. This construction allows light from the lightemitting element to outgo through a wide area. In addition, since thepair of metal plates project in directions different from each other,the light emitting device is stably fastened to terminals for powersupply. Additionally, since the metal plates ensure heat dissipation,reliability and stability are also improved. An LED chip, an LD chip andso on can be employed as the light emitting element 10. An LED chip inFIG. 1 is mounted on the transparent board 20 with a transparentdie-bonding member 52 by die-bonding.

Transparent Board 20

In the embodiment, the transparent board 20 has transmittance of 70% ormore for light from the light emitting element 10, and serves as asupport board that conducts heat generated by the light emitting element10 to the metal plates 30. The light emitting element 10 is secured onthe transparent board 20 with the transparent die-bonding member 52. Thetransparent die-bonding member 52 helps light to outgo through the lowersurface of the light emitting element 10, and allows the light to passthe die-bonding member 52 and the transparent board 20. Thus, the lightcan outgo. Sapphire, GaN, beryllium oxide (beryllia), ZnO, SiC, Si, ZnO,ZnS, Al, Cu, W, AlN, SiC, diamond, copper diamond, ruby, and singlecrystal or polycrystal of GaN, Si and so on can be employed as this heatconductive type of transparent board 20.

Particularly, in the case where a conductive material is employed as thetransparent board 20, a mount surface of the light emitting element 10can provide electrical connection. Only one of electrodes requires wirebonding. Accordingly, it is possible to reduce the number of wire lines44 and manufacturing cost, and to improve yields. From this viewpoint,it is possible to enhance improvement in reliability. Particularly, thewire lines 44 may be disconnected inside the resin that covers the wirelines 44 due to the difference in the thermal expansion coefficient, orthe like. Reduction of the number of the wire lines 44 that are usedinside the resin can reduce this risk.

It is preferable, in order to facilitate outgoing of light, that thelower surface of the transparent board 20 is a non-smooth surface. Inthis case, light can easily outgo through the lower surface. Forexample, the lower surface of the transparent board 20 is not polishedand remains as an irregular. Alternatively, stripes or dimples can beformed on the lower surface of the transparent board 20 on purpose. Inthe case where the transparent board 20 has the thus-formed lowersurface, even if a transparent member is not additionally disposed onthe lower side of the transparent board 20, light that passes the lowersurface of the light emitting element 10 can efficiently outgo. Inaddition, it is also preferable that the transparent board 20 has acurved lower surface. In this case, it is possible to reduce componentsof light that undergo total internal reflection at the lower surface ofthe transparent board 20. Therefore, it is possible to provide a lightemitting device with high light-outgoing efficiency.

In addition, in order to reduce reflection at the boundary between thelight emitting element 10 and the transparent board 20, it is preferableto adjust the refractive index difference between them. In the casewhere the light emitting element 10 has an element structure that issupported on a growth substrate, it is preferable that therefractive-index difference between the growth substrate and thetransparent board 20 is small. Alternatively, the refractive index ofthe growth substrate is smaller than the refractive index of thetransparent board 20. When materials for them are thus determined,reflection of light can be small. For example, in the case where thelight emitting element 10 has a semiconductor layer that is grown on asapphire substrate, sapphire is preferably used as the transparentboard. On the other hand, in the case where the light emitting element10 is a GaN group semiconductor element that does not have a growthsubstrate, a transparent board formed of GaN is preferably used.

Die-Bonding Member 52

In this embodiment, a material of the die-bonding member 52 is notspecifically limited, if it can secures the light emitting element 10 onthe transparent board 20, and can passes light from the light emittingelement 10. An organic material, such as thermoplastic resin andthermosetting resin, an inorganic material, and a hybrid material ofthem can be used. Specifically, epoxy resin as thermosetting resin,acrylic resin and polyimide resin as thermoplastic resin, and so on canbe given as examples. On the other hand, if the die-bonding member 52 iscolored due to deterioration caused by light, heat and so on, thelight-outgoing efficiency decreases. For this reason, the die-bondingmember 52 preferably has heat resistance, light resistance and heatconductivity. In addition, in order to adjust the thermal expansioncoefficient or electrical conductivity of the die-bonding member 52, afiller can be added to these resins.

Metal Plate 30

The metal plates 30 are inserted into the covering member 46 from sidesurfaces of the covering member 46, and are fastened to the transparentboard 20 so that the conductor member 22 is interposed between each ofthe metal plates 30 and the transparent board 20. The metal platespreferably have rounded corners that are located on edge sides thereofas shown in the metal plate 30B illustrated in the plan view of FIG. 3.In this case, it is possible to relieve residual stress after beingsecured to the transparent board 20. The metal plate 30 preferablyformed of an excellent heat conductive and electrical conductivematerial with surfaces that are plated with a metal capable ofreflecting light from the light emitting element 10.

Copper, Kovar (trademark) as alloy of iron, nickel and cobalt, an alloyof Kovar and copper, and so on can be given as examples of excellentheat conductive material. Since these materials have heat conductivityhigher than ordinary conductors, they can improve heat dissipation oflight emitting device and facilitate higher power output. In theembodiment, particularly, phosphor bronze is preferably used. Phosphorbronze has excellent corrosion resistance, wear resistance, platingcharacteristics, stress-and-corrosion cracking resistance, electricalconductivity and heat conductivity, and additionally has excellentprocessability in pressing, bending, drawing and so on.

In addition, prior to plating surfaces of the aforementioned material,it is preferable that copper strike plating is performed. In this case,oxides on the material are eliminated, and the material can be activatedand plated at a time. Accordingly, the material is coated with a copperfilm with good tackiness. Therefore, it is possible to improve metaladhesiveness on the whole surfaces of material, and additionally toimprove corrosion resistance. Additionally, the material metal isprevented from dissolution into a plating bath. Therefore, it ispossible to prevent contamination in the bath.

It is preferable that the material, which is thus subjected to surfacetreatment, is plated with a metal that can reflects light from the lightemitting element 10. Particularly, it is preferable that the material isprovided with a conductive film that has glossiness of 90 or more byplating. In this specification, glossiness is a value based on JISStandard that is represented by specular reflection factor in percentagewhen light from the light emitting element 10 is incident at 60° and ismeasured by VSR300A small surface color-difference meter manufactured ofNippon Denshoku Industries Co., Ltd. wherein the surface of a glass withrefractive index of 1.567 is defined as glossiness 0. Specifically, Au,Ag, Al, and so on, can be given as examples for plating main material.In addition, in the case where the metal plate 30 and the light emittingelement 10 are electrically connected with the metal wire lines 44, itis preferable that a main material for plating on the surface of themetal plate 30 is the same material as a main material with the metalwire lines 44.

The metal plate 30 has a substantially rectangular-shaped end that isconnected to the light emitting element 10 with the wire line 44, andthe other end that is exposed from the transparent member to be mountedto an external portion. In the light emitting device according to thisembodiment, the other end has a two-rectangular shape that has arectangle with the same width as the other end and a substantiallysquare shape with a width wider than the other end as shown in alater-discussed metal plate 30C illustrated in FIG. 14, or the like. Inthis construction, it is possible to improve heat dissipation toward andinstallation on the external portion. In addition, corners of thesubstantially two-rectangular shape are preferably rounded. This shapeprovides ease of handling of the light emitting device. Additionally, aplate screw opening 31 can be formed in a region with wider area in thetwo-rectangular shape to fasten the light emitting device to theexternal portion. In this case, the light emitting device can befastened to high thermally conductive metal or the like so as not tointerpose an organic material between them.

The metal plates 30 are disposed on right and left sides of the lightemitting element 10 and spaced away from each other at an interval, andare exposed from side surfaces of the covering member 46 that areopposed to each other. Thus, metal plates 30 can conduct heat from thelight emitting element 10 through the transparent board 20 toeffectively dissipate the heat externally. In the case where multiplelight emitting elements are mounted, in the case where a light emittingelement with positive and negative electrodes located on the samesurface side is mounted in a flip-chip manner, or the like, conductivelines with a width narrower than the light emitting element may bedisposed between the pair of metal plates. This construction can providevarious types of mount manners without cutting off light that is emittedfrom the light emitting element and outgoes through the lower surfacethereof. In addition, as discussed later, the metal plates 30 thatextend in a right-and-left direction serve as attachment portions thatare attached to a transparent bulb 60.

Conductor Member 22

The transparent board 20 and the metal plate 30 are welded. This weldingis conducted by using the conductor member 22 that is previously formedon the transparent board 20. It is preferable that the coat area of theconductor member 22 is smaller or larger than an adhesion surfacebetween the transparent board 20 and the metal plate 30. In other words,the adhesion surface preferably has a shape different from an alloy filmsurface. The reason is to reduce residual stress that is produced in thetransparent board 20 after welding. Therefore, it is possible to providehighly reliable light emitting device. Particularly, in the case wherethe coat area of the conductor member 22 is larger than the adhesionsurface between the transparent board 20 and the metal plate 30, it ispossible to reduce the aforementioned residual stress while keepingadhesive strength in check. For this reason, it is preferable that thecoat area of the conductor member 22 is larger than the adhesionsurface. The conductor member 22 is preferably formed of a thermalconductive material that can relieve the difference between the thermalexpansion coefficients of the transparent board 20 and the metal plate30. Specifically, tungsten, molybdenum or a mixture of copper and atleast one element of them is preferably employed. The conductor 22 ispreferably formed by printing.

In addition, it is preferable that the pair of conductor members 22occupy 20% to 50% of the surface of the transparent board 20. In thecase of more than 50%, light outgoing efficiency decreases, andadditionally the residual stress after the pair of conductor members 22are adhered to the transparent board 20 is large. In the case of lessthan 20%, the pair of conductor members cannot be adhered to thetransparent board 20 at enough adhesive strength. On the other hand,internal adhesion terminal portions of the pair of conductor membershave 20% to 50% of thickness relative to thickness of the transparentboard 20. In the case of less than 20%, the residual stress after thepair of conductor members are adhered to the transparent board 20 islarge. In the case of more than 50%, it is difficult that the pair ofconductor members are adhered to the transparent board 20 at enoughadhesive strength.

The die-bonding member 52 bonds the light emitting elements 10 and thetransparent board 20. A binder resin as an adhesive material bonds thetransparent board 20 and the conductor member 22. In addition, thermalconductivities at these boundaries can be maintained by improvement ofthermal conductivities of the die-bonding member 52 and the binderresin. For example, in the case where powder alumina or diamond is mixedin the binder resin, the thermal conductivity of the binder resin isimproved.

Covering Member 46

After the light emitting element 10 and the conductor members 22 aresecured on the transparent board 20, and the necessary wire lines 44 arefastened by bonding or the like, the covering member 46 formed of atransparent resin covers the periphery of them. A silicone resin, whichhas excellent heat resistance and light resistance, can be suitablyemployed as the covering member 46. In the illustration of FIG. 1, arectangular-parallelepiped-shaped silicone resin has a profile similarto the transparent board 20 located below the resin. The resin coversthe light emitting element 10 on the transparent board 20.

Second Transparent Member 40

A second transparent member 40 can additionally cover the coveringmember 46. FIG. 4 is a cross-sectional view showing a light emittingdevice 200 with the second transparent member 40 covering the coveringmember 46. In the case where the second transparent member 40 has around-shaped surface as shown in this Figure, light emitted from thelight emitting element can be radiated through the round-shapedtransparent member the without directivity. Particularly, the secondtransparent member 40 can serve as an optical lens. In this case, it ispossible to provide a light emitting device that can uniformly radiatelight in all directions. For example, the second transparent member 40can be formed of a silicone resin, an epoxy resin, glass, or the like.In addition, the second transparent member 40 can be formed in anycurved optical lens shape by transfer molding or the like.

On the other hand, it is not always necessary to form the secondtransparent member 40 in optical lens shape or other curved shapes suchas round shape. For example, as shown in a light emitting device 300 ofFIG. 5, a second transparent member 40B may have arectangular-parallelepiped shape. In the case ofrectangular-parallelepiped shape, there is an advantage that provideseasy molding. In addition, in construction that attaches the lightemitting device in the transparent bulb 60 as discussed later, thetransparent bulb 60 can serve as an optical lens. Therefore, there isalso an advantage that simplifies the construction of the transparentmember 40.

In addition, a wavelength conversion member 50 can be disposed aroundthe periphery of the light emitting element 10 as shown in FIG. 4 asnecessary. The wavelength conversion member 50 can absorb light emittedby the light emitting element 10 and convert its wavelength so as toemit luminescent radiation with different wavelength. A resin film orglass film containing a phosphor can be suitably used as this wavelengthconversion member 50. For example, in the illustration of FIG. 5, thewavelength conversion member 50B containing a phosphor is formed in afilm shape on the surface of the transparent member 40 as a wavelengthconversion film by coating. Thus, in the case where the transparentmember is uniformly formed on the curved surface of the optical lensshape, uniform mixture light can be obtained. Additionally, a phosphorcan be unevenly distributed in the wavelength conversion film dependingon the number and arrangement of light emitting elements to be used. Inother words, it is not necessary to provide the wavelength conversionmember around the whole periphery of the light emitting element. Thewavelength conversion member may be distributed so that a phosphor ishighly weighted in regions where a light amount is high such as upperand lower surfaces.

In addition, the second transparent member 40 can additionally serve asthe wavelength conversion member 50. For example, as shown in a lightemitting device 400 of FIG. 6, a phosphor 48 can be mixed into an epoxyresin as the transparent member 40C so that the transparent member 40Cserves as a wavelength conversion member. Alternatively, as shown in alight emitting device 400B of FIG. 7, a covering member 46B canadditionally serve as a wavelength conversion member. In other words, aphosphor 48 is mixed into a silicone resin that forms the coveringmember 46B so that the covering member 46B serves as both a coveringmember and a wavelength conversion member. In this case, it is possibleto provide an effect that reduces the number of production processes andproduction cost. Additionally, the wavelength of light emitted from thewhole surfaces including the lower surface in an LED chip can beconverted by mixture of the phosphor 48 not only into the coveringmember 46B but also into a die-bonding member 52B, lamination coating onthe periphery of the transparent board 20 with a phosphor film, or thelike. Alternatively, construction in which a wavelength conversion layeris formed by applying a phosphor on the interior surface of atransparent bulb is also applicable.

Transparent Bulb 60

Although a light emitting device 500, which is constructed as discussedabove, can be used alone, it can be attached to a lighting apparatus sothat it is easily handled for lighting application. FIG. 8 is across-sectional view showing the transparent bulb 60 with the lightingapparatus 500 according to the embodiment being disposed therein. Thetransparent bulb 60 is designed in a shape similar to a filament lampbut is provided with the lighting apparatus 500 instead of filament. Thetransparent bulb 60 is a light-bulb-shaped member that is composed oftransparent glass or the like. A pair of support leads 62 are disposedinside the transparent bulb 60. Ends of the pair of support leads 62 areprovided with slots that accommodate external connection terminalportions of the metal plates 30 of the light emitting device. As shownin an enlarged, perspective view of FIG. 9, in this illustration, theends of the support leads 62 have recessed portions 63. The metal plates30 are inserted into the recessed portions 63 and are fastened withscrews, or the like. For example, the metal plates 30 of the lightemitting device 500 is provided with plate-side screw holes 31B thatopen as shown in FIG. 9 to be fastened with the screws. On the otherhand, the support leads 62 are also provided with lead-side screw holes65 that are formed at locations corresponding to the plate-side screwholes 31B. As shown in FIG. 8, in the state where an LED chip of thelight emitting device 500 faces to a side surface of the light emittingelement 500, the metal plates 30 are inserted into the recessed portions63 so as to be located in place. Screws 66 are then inserted from ahorizontal side into the plate-side screw holes 31B and the lead-sidescrew holes 65 for threaded engagement. This engagement can ensureattachment of the light emitting device. Alternatively, even in the casewhere the support leads 62 are not provided with only the lead-sidescrew holes 65 without recessed portions, screws can be inserted intothe plate-side screw holes and the lead-side screw holes to attach thelight emitting device by threaded engagement. Attachment is not limitedto threaded engagement, needless to say, other methods such as rivet,caulking, welding, bonding, retainment, engagement and fit can be used.

In addition, since the LED chip is attached so that its upper surfacefaces a side surface of the transparent bulb, there is an advantage thatdirectly and outwardly directs light that outgoes through the upper andlower surfaces of the LED chip. In other words, in the case of aconventional LED, since light outgoes in one direction, a reflectionfilm or reflector is disposed. This construction tends to enhancedirectivity. For this reason, there is a problem this type of LED isunsuitable for lighting application that requires broad light emission.Additionally, the reflection film or reflector does not allow light tooutgo totally. In the case where the LED chip is oriented so that itsupper surface faces a side surface of the lighting apparatus, light thatoutgoes through the upper and lower surfaces of the LED chip is directedoutward as light output directly. Therefore, light from the LED chip caneffectively outgo. This construction can eliminate a reflector and soon, and provide an advantage in cost. Additionally, this constructioncan avoid the problems that lose light due to a reflection member andenhances directivity. An LED chip typically emits light through not onlyits upper and lower surfaces but also through its side surfaces. In thelight emitting device according to the embodiment, light that is thusemitted by the light emitting element effectively outgoes through allsurfaces. Therefore, it is possible to effectively radiate light throughthe side surfaces, and the upper and lower surfaces of the lightemitting device.

On the other hand, as shown in FIG. 10, the light emitting device can beattached so that the LED chip is oriented so that its upper surfacefaces the upper side of transparent bulb. In the light emitting deviceaccording to this embodiment, since light outgoes from the LED chipthrough all the peripheral surfaces such as the upper, lower and sidesurfaces, it is possible to provide broad light emission even in thecase where the light emitting device is oriented in any directions. Itis important to optimize elimination of a member that cuts off lightfrom the LED chip, that is, to bring the LED chip closer to a suspendedstate inside a light emitting apparatus such as transparent bulb so thatlight emitted through all the peripheral surfaces of the LED chip caneffectively outgo. This construction can provide a light emitting devicethat serves as a suitable lighting apparatus capable of illuminating awide area. In the illustration of FIG. 10, as shown in FIG. 11, the endsof the support leads 62B have recessed portions 63B. The metal plates 30are inserted into the recessed portions 63 and are attached with thescrews 66 that are inserted from the top side by threaded engagement orthe like.

In addition, the transparent bulb 60 is provided with a base 64 that canbe threadedly engaged with a conventional socket for light bulb.Terminals of the base 64 are connected to the support lead 62. The lightemitting element 10 of the packaged light emitting apparatus 500 isconstructed to be operated by power that is supplied to the terminals ofthe base 64. In this case, this light emitting device can be usedsimilarly to conventional light bulbs. Therefore, it is possible toeasily replace a conventional light bulb used in lighting with the lightemitting element. Particularly, the light emitting device, which employsan LED chip or the like, is operated at low power consumption and lessheat generation. Additionally, the light emitting device has long lifeas compared with filament lumps. As a result, maintenance such as bulbreplacement can be eliminated. The light emitting device is suitable forrequirements for resource savings and trash reduction. Therefore, thelight emitting device is very advantageous as next-generation lighting.

On the other hand, conventional light emitting elements such as LED havehigh directivity, and thus are not suitable in use as lighting thatprovides broad light emission. On the contrary to this, in the lightemitting device, the transparent board 20 that is provided the lightemitting element 10 mounted thereon passes light, and the transparentmember 40 is formed around all the peripheral surfaces of the lightemitting element 10. This construction allows light to outgo through allthe peripheral surfaces. Therefore, the light emitting device can beused for typical lighting application that provides broad lightemission.

In addition, the transparent bulb 60 can have various types of designedshapes as lighting. The transparent bulb 60 can have a shape similar toconventional light bulbs so that they are replaced by the transparentbulb, and, needless to say, can have special-purpose designed shapes.For example, the transparent bulb can have a cylindrical shape. Inaddition, a phosphor layer may be applied as a wavelength conversionmember on the interior surface of this cylindrical-shaped transparentbulb. In this lighting apparatus, the packaged light emitting devicethat is deposed therein does not include a wavelength conversion member,but a coating that is mixed with a phosphor is applied on the interiorsurface of the transparent bulb as a wavelength conversion member.Alternatively, both the packaged light emitting device and thetransparent bulb can have wavelength conversion members. Combination ofwavelength conversion members that include a plurality of phosphors canprovide two- or three-wavelength lighting, or the like, and thus canprovide a desired light color.

In addition, the transparent bulb can be filled with a filling material,or can be formed in solid by molding. The LED chip and phosphor areprotected from external stress, moisture, dust and so on by a fillingmember or molding. Particularly, in the case of a relatively smalllighting apparatus, since a molding amount is small, a problem thatincreases its weight does not arise. In this case, this type oftransparent bulb can be suitably used.

Support Lead 62

The support leads 62 are formed of an excellent electrically andthermally conductive metal such as stainless steel alloy, iron, copperand aluminum. On the other hand, the support leads 62 can be preferablyformed of the material as the metal plate 30. In the case where thelight emitting device 500 is electrically conductively and thermallyconductively attached to the support lead 62, the light emitting device500 is provided with power through the support leads 62, and heatgenerated in the light emitting device 500 is conducted to the supportleads 62 and is dissipated.

Alternatively, as shown in FIG. 12, metal plates 30D of a packaged lightemitting device 600 can be bent and extend so as to fastened to theinside of the base 63. In this case, the metal plates 30D serves as boththe metal plates and the support leads. Therefore, it is possible toreduce a parts count, and the number of production processes.

The chamber of the transparent bulb 60 can contain air. But the chamberof the transparent bulb 60 may be air-tightly enclosed and filled withan inert gas or maintained under vacuum. For example, in the case whereoxygen is eliminated from the chamber, it is possible to reducedeterioration due to oxidation of the metal plates 30 that project fromthe packaged light emitting device 500. In this case, it is possible toimprove reliability of the packaged light emitting device 500.

On the other hand, the support leads 62, which support the lightemitting device 500 and are disposed inside the transparent bulb 60, mayprovide detachable engagement of the light emitting device 500. In thiscase, a light emitting device with reduced output power can be replaced,or a light emitting device can be replaced by another packaged lightemitting device with different color light emission. This type of lightemitting device is more convenient.

In the case where the packaged light emitting device is thusaccommodated in the transparent bulb, it is not necessary to form thesecond transparent member that covers the light emitting element.

In the aforementioned illustrations, the metal plates 30 are disposed onthe transparent board 20 in substantially mirror images of each other,and are connected with wire lines 44. However, the metal plates 30 arenot limited to this construction. In the illustration of FIG. 1 or thelike, the light emitting element 10 has an insulating lower surface andan upper surface that is provided with n-side and p-side electrodes, andthus requires two wire lines 44. However, in the case where a lightemitting element has a lower surface that is provided with an electrode(e.g., n-side electrode), a transparent board can be formed of aconductive material. In this case, only one wire line, which isconnected to its upper surface, can provide electrical conduction.

Light Emitting Element 10

In this specification, light emitting elements such as LED and LD can beused as the light emitting element 10. In this embodiment of the presentinvention, a light emitting element with wavelength 550 nm or less,preferably 460 nm or less, and more preferably 410 nm or less is used asthe light emitting element 10. For example, an ultraviolet light LED,which emits light with wavelength of 250 nm to 365 nm as ultravioletlight, can be used. For example, an LED chip that emits ultravioletlight can be used as the light emitting element 10 so that thewavelength conversion member 50 converts the ultraviolet light intovisible light. In this specification, light is used in a sense thatincludes visible light and invisible light.

Various types of nitride semiconductors can be used as semiconductorlayers, which compose an LED or an LD. Specifically, a plurality oflayers that is formed of semiconductors such as In_(x)Al_(y)Ga_(1-x-y)N(0≤x, 0≤y, x+y≤1) are formed on a growth substrate by Metal-OrganicChemical Vapor Deposition (MOCVD), Hydride Chemical Vapor Deposition(HVPE), or the like. Generally, semiconductor layers grow on aparticular growth substrate, and thus form an LED. For example,well-known materials such as sapphire, spinel, SiC, GaN and GaAs can beused as growth substrate. In the case where an insulating substrate suchas sapphire is used, finally the insulating board may be removed.

In addition the main peak light emission wavelength of the lightemitting element 10 can be varied within a range between 420 nm and 490nm. Additionally, the light emission wavelength is not limited to theabove range, but a light emitting element with wavelength of 360 nm to550 nm can be used. Particularly, in the case where an ultraviolet LEDlight emitting device is employed for the light emitting device, theabsorption-and-conversion efficiency of excitation light can beimproved. Therefore, it is possible to reduce penetrating ultravioletlight.

Phosphor

A phosphor converts visible light or ultraviolet light that is emittedfrom the light emitting element 10 into light with different wavelength.In this case, the phosphor is used as a wavelength conversion material,which absorbs light and emits luminescent radiation with wavelengthlonger than the wavelength of absorbed light. Light emission of thelight emitting element 10 and the converted radiation are mixed to emitdesired color light externally. The phosphor is transparent, and isexcited by light emitted from a semiconductor light emitting layer ofLED, for example, and thus emits luminescent radiation. A YAG groupphosphor activated by europium, zinc sulfide coactivated by silver andaluminum, a nitride group phosphor such as alkaline-earthsilicon-nitride phosphor, and an oxynitride group phosphor such asalkaline-earth silicon oxynitride phosphor can be used as preferablephosphor. In addition, a phosphor that is excited by ultraviolet lightand emits luminescent radiation of a desired color may be used.

A phosphor that has the luminescent spectrum in a yellow, red, green orblue region due to excitation by light from the light emitting element10 can be used. In addition, a phosphor that has the luminescentspectrum in the intermediate color region of them, such as yellowishgreen, bluish green and orange, can be also used. Various combinationsof these phosphors can provide light emitting devices with various lightemission colors.

For example, a phosphor consisting of CaSi₂O₂N₂:Eu or SrSi₂O₂N₂:Eu,which emits green to yellow luminescent radiation, (Sr,Ca)₅(PO₄)₃Cl:Eu,which emits blue luminescent radiation, and (Ca,Sr)₂Si₅N₈:Eu, whichemits red luminescent radiation is used. In this case, it is possible toprovide a light emitting device that emits white light and has excellentcolor rendering. The reason is that, since red, blue and green of theprimary colors are used, variation of the composition ratio of first andsecond phosphors can provide desired white light.

The average particle size of phosphor is 3 μm or more, and preferably 5μm to 15 μm. Very small phosphor is classified and removed byclassification or the like so that particles with particle size of 2 μmor less occupy not more than 10% in volume distribution. Accordingly,light emission luminance can be improved. Additionally, chromaticityunevenness depending on light direction is reduced by reducing thenumber of particles with particle size of 2 μm or less.

In this case, the particle size means an average particle size that isobtained by an air permeation method. Specifically, the particle size isconverted as average particle size from a relative surface area valuethat is obtained based on pressure difference, under environmentalcondition at temperature of 25° C. and humidity of 70%, in a state whereair flows through a special tubular vessel at a constant pressure,wherein the vessel is provided with a sample of measured volume of 1 cm³that is packed therein. The phosphor used in the embodiment preferablyhas an average particle size of 2 μm to 8 μm. In addition, it ispreferable that phosphor particles with average particle size in thisrange are highly included. Additionally, particles are preferablydistributed in a narrow range. It is preferable that there are fewparticles with particle size not more than 2 μm. In the case where aphosphor with small particle size and less unevenness of particle sizedistribution is used, color unevenness can be reduced. Therefore, it ispossible to provide a light emitting device with an excellent colortone.

Wavelength Conversion Member 50

The wavelength conversion member 50 containing a phosphor is composed ofresin with the aforementioned phosphors mixed therein. A thermosettingresin can be used for phosphor-containing resin that composes thewavelength conversion member 50. It is preferable that the phosphor issubstantially uniformly contained in the phosphor-containing resin.However, a phosphor material may be unevenly mixed so as to partiallyexist. For example, a phosphor is distributed so that much of thephosphor material is included on the exterior surface side of thephosphor-containing resin. In this case, much of the phosphor is spacedaway from a contact surface between the light emitting element 10 andthe phosphor-containing resin, thus, heat generated by the lightemitting element 10 is less prone to conducted to the phosphor.Therefore, it is possible to suppress deterioration of the phosphor. Asilicone resin composition, a denatured silicone resin composition orthe like is preferably used as the phosphor-containing resin. However, atransparent, insulating resin composition such as epoxy resincomposition, denatured epoxy resin composition and acrylic resincomposition or the like can be used. In addition, pigment, diffusionagent and so on can be mixed into the phosphor-containing resin.

It is preferable that the phosphor-containing resin is soft even aftercuring. Before curing, it is preferable that the phosphor-containingresin is liquid with low viscosity. The reason is that thephosphor-containing resin spreads over the periphery of the lightemitting element 10, and that the phosphor-containing resin fillsinterstices except that electrical connection parts between the lightemitting element 10 that is mounted in a flip chip manner and leadterminals. In addition, the phosphor-containing resin preferably hasadhesiveness. In the case where the phosphor-containing resin hasadhesiveness, it is possible to improve adhesion between the lightemitting element 10 and the transparent board 20. The resin that hasadhesiveness includes not only a material that provides adhesiveness atroom temperature, but also a material that provides adhesiveness whenpredetermined heat and pressure are applied to the phosphor-containingresin. Additionally, in order to improve the adhesive strength, thephosphor-containing resin can be subjected to heat or pressure, or canbe dried.

Diffusion Agent

In addition, a diffusion agent can be added to the phosphor-containingresin in addition to a phosphor. Specifically, barium titanate, titaniumoxide, aluminum oxide, silicon oxide, and so on, can be suitably used asthe diffusion agent. In this case, it is possible to provide a lightemitting device with suitable directivity.

In this specification, the diffusion agent refers to a material that hasa center particle size not less than 1 nm to less than 5 μm. Thediffusion agent of not less than 1 nm to less than 5 μm excellentlyscatters light from the light emitting element 10 and phosphor, and thussuppresses color unevenness that tends to appear in the case where aphosphor with a large particle size is used. For this reason, this typeof diffusion agent is suitably used. In addition, the spectralhalf-value width in light emission can be narrow. Therefore, it ispossible to a light emitting device with high color purity. A diffusionagent of not less than 1 nm to less than 1 μm has a small interferenceeffect on the wavelength of light from the light emitting elements 10,but has high transparency, and additionally can increase viscosity ofresin without reduction of luminous intensity.

Filler

In addition, a filler can be added to the phosphor-containing resin inaddition to a phosphor. Specifically, materials similar to the diffusionagent can be used as a material of the filler. But, the filler has acenter particle size different from the diffusion agent. In thisspecification, the filler preferably has a center particle size of notless than 5 μm to not more than 100 μm. In the case where a transparentresin contains this type of filler, chromaticity unevenness of the lightemitting device can be improved by light dispersion, and additionallythermal shock resistance of the transparent resin can be improved.Accordingly, it is possible to provide a highly reliable light emittingdevice that can prevent disconnection of wire lines 44 that connectlight emitting element 10 and external terminals, detachment of thebottom surfaces of the light emitting element 10 from the bottom surfaceof the recessed portion of the package, and so on, even in use underhigh temperature. Additionally, the resin can be adjusted so as to haveconstant flowability for a long time. As a result, a sealing resin canbe formed in a desired location. Therefore it is possible tomass-produce the light emitting devices at high yield.

In the case where the thus-constructed light emitting device is used, itis possible to provide a high degree of flexibility in designing, andthus to provide various types of designs. For example, a light emittingdevice 700 in a form shown in FIG. 13 can be constructed to satisfyfunctions or designs required in lighting applications. In the lightemitting device 700 shown in FIG. 13, an optical lens 40D is disposedonly on the lower side of the transparent board 20. Light that passesthrough the transparent board 20 can outgo in a light emitting element10 mount direction. In this construction, light that outgoes in variousdirections can be directed in one direction. Therefore, it is possibleto provide a light emitting device that can emit light at highluminance.

Although the light emitting device is constructed so that the wavelengthconversion member 50 is located around the light emitting element 10 inthe foregoing illustration, a light emitting device that does not have awavelength conversion member can be constructed so as to emit light fromthe light emitting device directly as it is. For example, a blue,yellow, green lighting device or the like that includes a blue, yellowor green LED can be provided.

The light emitting device that includes single LED chip is discussed inthe foregoing illustration. However, a plurality of the light emittingelements 10 can be used. For example, as shown in a plan view of FIG.14, a light emitting device 1200 includes four LED chips 10C. Two LEDchips among the LED chips 10C are connected in serial as one set betweena pair of metal plates 30C. Two sets in which the two LED chips 10C areconnected in serial are electrically connected in parallel. In thiscase, it is possible to increase output power. In addition, as shown ina plan view of FIG. 15, a light source can have a plurality of LED chips10D that aligns in a line that extends in a filament-longitudinaldirection. In illustration of FIG. 15, twelve LEDs 10D align in thehorizontal direction. Six LEDs among them are connected in serial as oneset. Two sets in which the six LEDs of them are connected in serial areconnected in parallel. Additionally, in order to provide easy connectionby wire-bonding, lead regions 23 extend from respective conductormembers 22D in proximity to the center of the light source. Moreover, asshown in FIG. 16, common lead region 23B may be independently disposedthe center of light source so that LED chips 10E are connected to thecommon lead region 23B by wire-bonding.

According to this embodiment, it is possible to provide a lightingapparatus that uses the light emitting element 10 and thus has highperformance. In conventional light emitting devices, an LED chip ismounted on the metal plate 30, thus, there is a problem that cuts offlight that travels downwardly by the conductor 22 member. On thecontrary to this, the lower surface light emission region of the lightemitting element 10 is not disposed directly on the conductor member 22.In other words, the conductor members 22 are not located so as to facethe upper and lower surfaces as the largest surfaces of LED chip thatcomposes the light emitting element 10, but the conductor members 22 arelocated on the side-surface sides of the LED chip. This arrangementallows light to outgo downwardly.

Generally, since an insulating board is used as a board that is providedwith the light emitting element 10 mounted thereon, this type of boardhas poor heat conductivity, and thus provides insufficient heatdissipation. If this type of light emitting element 10 is enclosed in aglass bulb as it is, temperature rises, thus, its reliability decreases.In this embodiment, the light emitting element 10 is disposed on thetransparent board 20, thus, its heat conductivity and heat dissipationare improved. In addition, in the case where the transparent board 20 iselectrically conductive, this construction provide great improvement ofheat conductivity. Thus, the light emitting element 10 with high outputpower can be stably used. Therefore, it is possible to provide highperformance and high reliability.

A light emitting device according to the embodiment can be applied to alight source for lighting, an LED display, a back light source, a signallight, an illuminated switch, various sensors, various indicators and soon, which have a blue or ultraviolet light emitting diode as a lightsource and has excellent white light emission, for example. A method forproducing can be applied to them.

It should be apparent to those with an ordinary skill in the art thatwhile various preferred embodiments of the invention have been shown anddescribed, it is contemplated that the invention is not limited to theparticular embodiments disclosed, which are deemed to be merelyillustrative of the inventive concepts and should not be interpreted aslimiting the scope of the invention, and which are suitable for allmodifications and changes falling within the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:
 1. A light emitting device comprising: a boardhaving a first surface and a second surface opposite to the firstsurface, the board being longer in a first direction than in a seconddirection perpendicular to the first direction in a plan view, the firstsurface having a first end portion and a second end portion opposite toeach other in the first direction; a plurality of light emittingelements mounted on the first surface of the board, the plurality oflight emitting elements arrayed in a row along the first direction; awavelength conversion member adapted to convert wavelength of lightemitted from the plurality of light emitting elements, the wavelengthconversion member including a first portion covering the plurality oflight emitting elements and a second portion covering the second surfaceof the board in a cross-sectional view; a first metal plate disposed onthe first end portion of the board; and a second metal plate disposed onthe second end portion of the board, wherein the plurality of lightemitting elements includes: a first light emitting element locatedclosest to the first metal plate among the plurality of light emittingelements, and a second light emitting element located closest to thesecond metal plate among the plurality of light emitting elements,wherein the first metal plate is electrically connected to the firstlight emitting element via a wire, the first metal plate having: a firstend surface facing the first light emitting element, and a second endsurface opposite to the first end surface and exposed from thewavelength conversion member, wherein the second metal plate iselectrically connected to the second light emitting element via a wire,the second metal plate having: a first end surface facing the secondlight emitting element, and a second end surface opposite to the firstend surface and exposed from the wavelength conversion member, andwherein the plurality of light emitting elements on the first surface ofthe board is located between the first end surface of the first metalplate and the first end surface of the second metal plate.
 2. The lightemitting device according to claim 1, wherein, in a plan view, each ofthe first metal plate and the second metal plate is longer in the firstdirection than in the second direction.
 3. The light emitting deviceaccording to claim 1, wherein, in the plan view, a maximum width of thefirst metal plate in the second direction and a maximum width of thesecond metal plate in the second direction are larger than a width ofeach of the plurality of light emitting elements in the seconddirection.
 4. The light emitting device according to claim 1, wherein,in the plan view, a maximum width of the first metal plate in the seconddirection and a maximum width of the second metal plate in the seconddirection are larger than a width of the board in the second direction.5. The light emitting device according to claim 1, wherein the board isconfigured to be transparent so that light emitted from the plurality oflight emitting elements on the first surface of the board forwardsoutside of the light emitting device through the second surface of theboard.
 6. The light emitting device according to claim 1, wherein theplurality of light emitting elements is electrically connected inseries.
 7. The light emitting device according to claim 1, wherein thewavelength conversion member contains a YAG group phosphor, a nitridegroup phosphor, or an oxynitride group phosphor.
 8. The light emittingdevice according to claim 1, wherein the plurality of light emittingelements comprises a nitride semiconductor.
 9. The light emitting deviceaccording to claim 8, wherein the plurality of light emitting elementscomprises In_(x)Al_(y)Ga_(1-x-y)N (0≤x, 0≤y, and x+y≤1).
 10. The lightemitting device according to claim 1, wherein the plurality of lightemitting elements is configured to emit light having a wavelength in arange of 360 to 550 nm.
 11. The light emitting device according to claim1, wherein the wavelength conversion member has a curved surface. 12.The light emitting device according to claim 1, wherein the lightemitting device is configured to be installed in a bulb.